Engine fuel control



March 30, 1954 F. c. REGGIO ENGINE FUEL CONTROL Original Filed Nov. 4, 1943 Patented Mar. 30, 1954 ENGINE FUEL CONTROL Ferdinando Carlo Reggio, Norwalk, Conn.

Original application Nov Divided and 508,897. 13, 1952, Serial No.

ember 4, 1943, Serial No. this application October 314,470

36 Claims. (Cl. 123-140) This invention relates to fluid flow regulating systems and more particularly to fuel metering and control systems for combustion engines, this application being a division of applicant's copending application Serial No. 508,897 filed November 4, 1943, for Fuel Supply System.

The invention is particularly adapted for aircraft propulsion powerplants operating under varying conditions of barometric pressure, ambient temperature, thrust and speed.

An object of the invention is to provide an improved engine fuel control which automatically and under all operating conditions whether steady or transient maintains the ratio between engine fuel flow and engine air flow within predetermined upper and lower limits.

Another object is to provide an improved engine fuel control which automatically so regulates the fuel feed as to secure at all times proper com bustion mixtures and maintain the temperatures resulting from combustion within desired safe limits.

The above and other objects will be apparent as the description proceeds. In the following description and in the claims various details will be identified by specific names for convenience, but they are intended to be as generic in the application as the art will permit.

The drawing, which shows an example of embodiment of the invention, is a sectional elevational view of a fuel metering device and diagrammatically indicates the connections thereof with the engine and the fuel nozzle valves.

In the specific embodiment of the invention which is here described, the engine 80 is shown as an internal combustion engine provided with an air induction system comprising a passage having an orifice or venturi 94 therein, a valve 95 and an engine-driven compressor 99 delivering air under pressure to a manifold 91 connected with the cylinder inlet ports leading to the combustion chambers.

The fuel system comprises an engine-driven fuel pump 41 which is supplied with liquid fuel at suitable pressure from a conduit 8| through an orifice 82 whose effective area is controlled by a slide valve-83. The pump discharges fuel, always in excess of engine requirements, to the supply manifolds 45.

A number of fuel injectors 9 are provided, each having an intake port connected with one of the fuel supply manifolds 45, a nozzle valve through which fuel is delivered to the engine in quantity variable with the fuel pressure, and a return port in free communication with the inlet port and connected with one of the return manifolds 39 through which the excess fuel is circulated back to the inlet side of the pump 41, as described hereinafter. These fuel injectors or nozzle units 9 are no part of the present invention. One suitable type thereof, designed for intermittently discharging fuel into the engine cylinders is described and claimed in applicants Patent No. 2,516,828 issued July 25, 1950. Another suitable type of injector or nozzle, well known in the art, consists essentially of a calibrated orifice through which a continuous spray of fuel is injected into the air stream in the engine air induction system or manifold.

The excess fuel which fiows from the injection units 9 to the return manifolds 39 is led to a pressure regulating device or by-pass device 84 having a slidable valve 85 w -ch controls a flow restricting orifice 81 through which the excess fuel flows back to the intake side of the pump 41, downstream of the orifice 82. The fuel flow through the latter orifice is thus equal to the engine fuel flow.

The valve 85 is actuated sponsive diaphragms 89 and 90. By means of conduits 9| and 92 the fuel pressure upstream and downstream of the orifice 82 is brought to bear on opposite sides of the former diaphragm, thus applying to the valve 85 an axial load which increases with the engine fuel supply, in a direction to increase the effective area of the orifice 81.

The flexible diaphragm 90, connected at its center with the valve 85, has a cup-shaped outer portion whose periphery is secured to a co-operating cup-shaped member IUI connected with the resiliently loaded piston I 02 of a hydraulic servomotor I03 controlled by a Venturi air density responsive bellows I04. By means of a conduit I05 and passages I01 and I08 the Venturi differential pressure is brought to bear on opposite sides of the diaphragm 99, thus transmitting to the valve 85 a load which increases with the Venturi air flow and tends to shift the valve in a direction todecrease the open area of the pressure regulating orifice 81. A bellows I09 connected with the cup member I0! serves to define higher and lower air pressure chambers within the diaphragm housing. The cup-member ml and the diaphragm 90 are so designed that as the former slides towards the latter, an increasing annular outer portion of the diaphragm is caused by the air pressure differential to come into contact with the 'member I 0|, thereby decreasing the diaphragm area which is effective as pressure responsive means for the actuation of the valve 90. The effective diaphragm area is thus variably adjustable and is dependent upon the position of the piston I02.

Fluid under pressure. for example lubricating by two pressure reoil from the engine, continuously flows into the cylinder chamber III through a small flow restricting orifice I I2. This oil leaves the cylinder chamber through another orifice II3 formed in the piston I02 and controlled by a needle valve H4 connected to the bellows I04. Thus the piston constantly follows the needle H4 at definite distance therefrom without exerting any reaction on the bellows IE4; when the latter contracts, the open area of orifice H3 increases, the oil pressure in chamber I I I drops, and the piston spring plus the differential air pressure on member IOI move the piston I02 toward the bellows. Conversely, when the latter expands, the effective area of orifice H3 decreases, and the increasing oil pressure in chamber III moves the piston away from the bellows.

The bellows I04 contains a definite mass of air or gas, and the walls thereof are so highly fiex ible as to expand or contract within the designed limits under negligible load. This bellows is surrounded by induction air in the immediate vicinity of the venturi, the air within the bellows thus being at the same pressure and temperature as the air flowing through the venturi, and therefore having the same density. As a result, the volume and in turn the length of the bellows are inversely proportional to the Venturi air density.

The mass air flow per second W through the venturi may be calculated by the following formula where 6 is the Venturi air density and I is the Venturi pressure differential. In the above formula and in the following ones K represents various constants dependent upon the geometrical unchanging dimensions of the metering elements and, in some of the formulae, also upon the fuel density.

The load P applied to the valve 85 by the diaphragm 90 is 2 P=KD I:KD

wherein D is the effective diameter of the diaphragm, that is, the diameter of the portion thereof which is not in contact with the cupmember IOI.

On the other hand the fuel flow per second w through the orifice 82 is w=Ks /i where s is the variable effective area of the orifice 82, and i is the fuel pressure drop across the orifice. The load transmitted to the valve 85 by the diaphragm 89 is The diaphragm 90 and the cupmeipberl [H are so designed that as the Venturi air density varies and the bellows I04 expands or contracts and shifts the cup member, the effective diameter of the diaphragm varies proportionally to the square root of the air density, thus rendering the fraction D/ /6 constant. The fuel-air ratio then becomes w/W=Ks, in other words this ratio is determined by the adjustment of the needle valve 83 exclusively, irrespective of changes of altitude within the designed limits.

The profile of the cup member IOI and diaphragm 90 may readily be designed to satisfy the above requirement. If the axial length of the bellows I04 when subject to standard sea level air density is L, and the corresponding predetermined eifective diameter of the diaphragm is d, at high altitude where the Venturi air density is one half of the standard sea level value the length of the bellows is 2L, and owing to the changed position of the cup member relative to the diaphragm, the effective diameter of the latter will have to be 0.707 d. At higher altitude where the Venturi air density is one fourth of the standard sea level value, the length of the bellows is 4 L, and the effective diameter of the diaphragm will be 0.5 11.

Manual as well as automatic control of the valve 83 may be provided to regulate the engine fuel-air ratio. Four cams are shown in the drawing for actuating this valve. The cam H5 is manually controlled by means of suitable linkage means. Cam H1 is connected to a manifold air pressure responsive bellows H8. Cam H9 is actuated in dependence upon the engine speed by a resiliently loaded diaphragm I20 responsive to the fuel pressure drop determined by an orifice I2I provided on the discharge side of the volumetric engine-driven pump 47, and cam I22 is actuated by a bellows I23 connected with an element I24 responsive to the manifold air temperature and preferably also responsive in predetermined degree to the engine cylinder temperature. The number, character and arrangement of the automatic devices connected with the fuel-air ratio control valve 83 may of course be varied to suit specific characteristics of various types of engines.

In operation, the fuel discharged under pressure by the pump 41 is led through the supply manifolds 45 to the various injectors 9; part of it is delivered to the engine, and the excess returns to the inlet port of the pump 41 through the return manifolds 39 and the by-pass orifice 8! controlled by the valve 85. When the valve is set in its extreme left position, with the by-pass orifice 81 fully open, no appreciable amount of pressure is set up on the discharge side of the pump 41 or within the injectors 9, and the latter therefore do not deliver any fuel to the engine; the fuel discharged by the pump 41 is all returned to the inlet port thereof, no new fuel is admitted from the tank through the inlet pipe 8|, and therefore no pressure drop is set up across the restriction 82 controlled by the valve 83. On the other hand, when the same valve 85 is in its extreme right position, reducing to a minimum the open area of the orifice 81, the pressure of the fuel on the discharge side of the pump 41 and in the injectors 9 attains its maximum value, the injectors 9 deliver to the engine their maximum designed fuel flow, and the flow of fuel from the tank through the restriction 82, and therefore the pressure drop across said restriction, attain their maximum value. ,It is thus cl ar th t the. valve. 85 variably controls.

ae'rasse air flow; and any variation in the Venturi difthe speed of the engine is accompanied by a corresponding variation in engine air flow, it follows that any variation in engine speed will cause operation of the valve 85.

These embodiments of the invention have been shown merely for purpose of illustration and not as a limitation of the scope of the invention. It is therefore to be expressly understood that the invention is not limited to the specific embodiment shown, but may be used in various other ways, in connection with other types of prime movers, that various modifications may be made to suit different requirements, and that other changes, substitutions, additions and omissions may be made of operations of the parts Without departing from the limits or scope of the invention as defined in the following claims.

In interpreting the claims, where they are directed to less than all of plete systems disclosed, they are intended to cover possible the recited elements in installathe non-recited elements. Certain features claimed herein are disclosed in my application Serial No. 401,353 filed July '7, 1941, now Patent No. 2,378,036 issued June 12, 1945.

I claim:

1. In a system for controlling the flow of liquid fuel to the combustion chamber of an engine, means defining a flow passage for the fuelhaving a variable feed restriction therein, a first valve for selectively varying the area of said restriction to accelerate and decelerate the engine, a speed governor arranged to be driven from the engine for actuating said first valve, a regulator valve movable to different positions to control the metering head across said restriction, means for automatically varying the position of Said regulator valve with changes of engine speed, and means responsive to changes in pressure of the air flowing to the combustion chamber for modifying the action of the regulator valve.

2. In a system for controlling the flow of liquid fuel to the combustion chamber of an engine having an engine driven compressor for supplying air under pressure to the combustion chamber, means defining a flow passage for the fuel having a variable feed restriction therein, a first valve to selectively vary the area of the restriction, a speed governor for actuating said first valve, a regulator valve movable to different positions to adjust the metering head across said restriction, pressure responsive means connected to the regulator valve, means for automatically producing a differential across said pressure responsive means varying with variations in engine speed, and means responsive to changes in pressure of the air flowing to the compressor for modifying said differential.

3. In a system for controlling the flow of liquid fuel to an engine having a. compressor supplying a flow passage striction, a manually operable member operatively connected to said valve, an engine driven speed governor also having an operative connection with said valve, a regulator valve movable to different positions to adjust the metering head and deceleration, and means responsive to changes in pressure of the air flowing to the compressor for modifying said differential.

4. In a system for controlling the fiow of liquid restriction, pressure responsive means connected to said regulator valve, means creating a force on said pressure responsive means in a direction tending to increase the flow of fuel through said restriction varying with variations in engine speed, and means for subjecting said pressure refiow of fuel through said restriction.

5. A system as claimed in claim 4 wherein means are provided for pressurizing fuel to said regulator valve including an engine driven supply pump.

6. In a system for controlling the flow of liquid fuel to a combustion engine having an engine driven compressor for supplying air under pressure for combustion, means defining a flow passage for the fuel having a variable feed restriction therein, a first valve for varying the area of said restriction, means arranged to be responsive to engine speed and manual supervision for con trolling said valve, a regulator valve varying the flow of fuel through said restriction, diaphragm means connected to said regulator valve, means arranged to produce a force varying with varialator valve in a direction to increase the flow of fuel through said restriction and said diaphragm to the compressor for modifying the regulating differential produced across said diaphragm means. 7

7. In a system for controlling the fiow of fuel to an engine, means defining a flow passage for the fuel having a metering restriction therein, a valve for varying the area of said restriction, a

8. In a system for controlling the flow of liquid fuel to an engine having an engine driven compressor for supplying air under pressure, means defining a flow passage for the fuel having a variable feed restriction therein, a valve to selectively vary the area of. the restriction, a speed governor actuating said valve, a regulator valve movable to different positions to adjust the metering head across said restriction, pressure responsive means connected to the regulator valve, means for automatically producing a differential across said pressure responsive means varying With variations in engine speed, and means responsive to changes in temperature of the air flowing to the compressor for modifying said differential.

9. In a system for controlling the flow of liquid fuel to an engine having an engine driven compressor for supplying air under pressure, means defining a flow passage for the fuel having a variable feed restriction therein, a valve for varying the area of said restriction, a manually operable member operatively connected to said valve, an engine driven speed governor also having an operative connection with said valve, a regulator valve movable to different positions to adjust the metering head across said restriction, pressure responsive means connected to the regulator valve, means for subjecting said pressure responsive means to a differential varying with variations in engine speed to automatically maintain the rate of fuel feed within predetermined limits during acceleration and deceleration, and means responsive to changes in temperature of the air flowing to the compressor for modifying said differential.

10. In a system for controlling the flow of fuel to an engine, means defining a flow passage for the fuel having a metering restriction therein, a valve for varying the area of said restriction, a governor adapted to be driven by the engine and operatively connected to said valve for automatically positioning the same, manual means operable at the will of a pilot for varying the adjustment of said valve, and means responsive to changes in temperature of the air fiowing to the engine for automatically varying the meter ing head across said metering restriction at any given position of the valve.

11. In a system for controlling the fiow of liquid fuel to'an engine, means defining a flow passage for the fuel having a variable feed restriction therein, a first valve for selectively varying the area of said restriction, speed responsive means arranged to be driven from the engine for actuating said first valve, a regulator valve movable to different positions to control the metering head across said restriction, means for automatically varying the position of said regulating valve upon changes of engine speed, and means responsive to changes in temperature of the air flowing to the engine for modifying the action of the regulator valve.

12. In a system for feeding fuel to an engine, a conduit supplying fuel to said engine, a metering restriction in the conduit, means for regulating the pressure drop across the restriction, and means for automatically varying the effective area of the restriction with changes in engine speed.

13. In a system for supplying liquid fuel to an engine, one or more fuel discharge'nozzles, a pump for supplying fuel under pressure to said. nozzles, a fuel conduit communicating said pump with said nozzles and. having a metering restriction therein upstream of the nozzles, adjustable valve means for varying the flow through said restriction, manual means for adjusting said valve means, an engine driven governor operatively connected to said valve means for automatically adjusting the. latter, and means reponsive to, changes: in; the: pressurepf the. air.

flowing to. the engine arranged; to' adjust the flow through said restriction independently of said governor.

14. In an engine fuel control having a fuel passage, a restriction therein, first means movable to control the effective area of said restriction, second means for regulating the pressure head across said restriction, means actuating said second means to vary said pressure head under varying values of engine air flow so as to maintain for each setting of said first means a corresponding substantially constant fuel to air ratio, and means including manually operable means and engine speed responsive means for variably positioning said first means Within a predetermined range of motion to vary the fuel to air ratio within predetermined rich and lean limits.

15. Regulating apparatus for a powerplant including a fuel feeding system, a fuel feed valve therein, a governor or like speed responsive device for actuating said valve, and means responsive to variations in air pressure for regulating the pressure head across said valve.

16. Regulating apparatus for a poiverplant including a fuel feeding system, a fuel feed valve therein, a governor or like speed responsive device for actuating said valve, and means responsive to variations in air temperature for regulating the pressure head across said valve.

17. Regulating apparatus for a powerplant including a fuel feeding system, a fuel feed valve therein, a governor or like speed responsive device for actuating said valve, and means responsive to variations in air density for regulating the pressure head across said valve.

18. Regulating apparatus for a powerplant including a fuel feeding system, a fuel feed valve therein, a governor or like speed responsive device for actuating said valve, and means responsive to variations in operating conditions affecting power-plant air fiow for regulating the pressure head across said valve.

19. Regulating apparatus for a powerplant including a fuel feeding system, a fuel feed valve therein, a governor for actuating said valve, and means for regulating the pressure head across said valve in accordance with powerplant air flow.

20. For use in a fuel supply system for powerplants having a combustion space to which air is supplied under pressure, a fuel conduit having a variable metering restriction therein, means for creating a flow of fuel through said conduit, an element for varying the area of said restriction, a governor driven from said powerplant and operatively connected to actuate said element, a regulating valve arranged to vary the fiow of fuel through said restriction, pressure responsive means operatively connected to said valve and arranged to respond to the drop across said restriction, means for regulating the pressure differential across said pressure responsive means, and means responsive to changes in pressure of the air flowing to the combustion space for modifying the differential across said pressure responsive means.

21. For use in a fuel supply system for powerplants having a combustion space to which air is supplied under pressure, a fuel conduit having a variable metering restriction therein. means for creating a flow of fuel. through said conduit, an element for varying the area of said restriction, a governor driven from said powerplant. and. operativelyconnected to actuate said element, a regulating valve arranged to vary the flow of fuel through said restriction, pressure responsive means operatively connected to said valve and arranged to respond to the drop across said restriction, means for regulating the pressure differential across said pressure responsive means, and means responsive to changes in temperature of the air flowing to the combustion space for modifying the differential across said pressure responsive means.

22. A device for regulating the fuel feed of aircraft powerplants, comprising a fuel conduit having a feed restriction therein, a feed valve controlling said restriction, means for actuating said feed valve including a control member and a governor driven from the powerplant,

across said feed valve, and means for varying said differential in relation to changes in entering air density.

23. In a fuel control device for controlling the flow of fuel to the combustion space of a powerplant having a prime mover, a fuel supply conduit, a first valve in said conduit, a governor arranged to be driven by said prime mover for controlling said first valve, a by-pass valve arranged to regulate the fuel metering head across said space for actuating said by-pass valve.

24. An engine fuel supply system including an adjustable metering valve, an adjustable pressure regulating valve in series with said metering valve, an engine-driven positive displacement pump having an outlet duct with a constriction therein located to pass the whole output of said pump, a pressure responsive member sensing variations in pressure difference across said constriction, and means connecting said pressure responsive member to said metering valve to actuate the latter upon changes in said pressure difference.

25. In or for a thermal powerplant having a first system for the supply of a first fluid and a second system for the supply of a second fluid, a fluid flow control orifice in said first system, a valve for controlling said orifice, a first device responsive to a speed condition of the powerplant and a second device responsive to pressure in a portion of said second system for positioning said valve, a by-pass valve for controlling the pressure drop across said orifice, said by-pass valve having wall means movable therewith for subjecting the by-pass valve to actuating pressures operating in opposite directions, connections from the upstream and downstream sides of said orifice to opposite sides of said wall means for positioning the by-pass valve in accordance with the difference in pressure across said orifice, and a spring connected to bias said by-pass valve in a direction assisting the pressure on the downstream side of the orifice.

26. In a valve control system for fluid delivery apparatus for a thermal powerplant, a fluid flow control orifice, a valve for controlling said orifice, a first device responsive to a speed condition of the powerplant and a second device responsive to a temperature condition of the powerplant for positioning said valve, a by-pass valve for controlling the pressure drop across said orifice, said by-pass valve being provided with movable wall means for subjecting the by-pass valve to pressup ing said valve, first pressur responsive means subject to the difference in pressure between a point upstream of said orifice and a point downstream thereof, a second valve for varying the pressure head across said orifice, a second system for supplying another fluid to said powerplant, Venturi means in the second system, second pressure responsive means subject to the Venturi differential pressure, and an operative connection for actuating the second valve from said first and second pressure responsive means.

28. For an engine having an air intake system with a Venturi therein and a fuel supply system comprising a plurality of fuel discharge units and fuel conduit means interconnecting said units, a control device comprising an orifice for metering the fuel flow to said units, a first valve for controlling said orifice, engine speed responsive sponsive means and intake air pressure and temperature responsive means for actuating said second valve.

29. In a thermal powerplant having a first fluid supply system, a second fluid supply system, a valv controlling a metering orifice in the first fluid supply System, a device responsive to a speed powerplant, a device responsive level in said powerplant and a responsive to pressure in a portion of said fluid supply system for actuating said valve, 9, by-pass valve movable to control the pressure head across said orifice, and conduit means for subjecting said by-pass valve to the pressure difference between upstream and downstream sides of said orifice.

sponsive means for actuating said second valve.

31. For an engine having a supercharger, an intake system leading air to the supercharger, a manifold leading air from the supercharger to the engine cylinders, and Venturi means in said intake system: a fuel supply system including a fuel passage; a flow restricting orifice in said passage; a first valve controlling said orifice; engine speed and temperature responsive means and manifold pressure responsive means for actuating said valve; 2. second valve for controlling the pressure head across said orifice; and means responsive to Venturi differential pressure and means responsive to pressure difference between spaced points of said fuel supply system for controlling said second valve.

32. For an engine having at least one combustion chamber, an air induction system with a 30. For an engine having an air induction syspump for supplying agave Me compressor therein for supplying air to said combustion chamber and a fuel system with a pump thereinrfor supplying fuel-to said combustion chamber: a fuel control device including a fuel passage with a fiow restricting orifice therein; a first valve for controlling said orifice; manually operable means, engine speed responsive means, engine temperature responsive means and means responsive -to pressure in a portion of said air induction system for actuating said valve; a second valve for regulating the-pressure headacross said orifice; andconduit'means for subjecting-said second valve to the pressure in a portion of said fuel system upstream of said orifice and to the pressure in a portion of the same system downstream of said orifice.

33. In a system for supplying liquid 'fuel to an engine, one or more fuel discharge nozzles, a fuel under pressure to said nozzles, a fuel conduit communicating said pump with said nozzles and having a metering restriction therein upstream of the nozzles, adjustable valve means for-varying the flow-through said restriction, manual means for adjusting said valve means, an-engine driven governor operatively connectedto said'valve means -for automatically adjusting the-latter and means responsive to changes in the'temperature of the air flowing to the engine arranged to adjust the flow throughsaid restriction independently of said governor.

34. In-a system for supplying liquid fuel to an engine, one or more 'fuel discharge nozzles, a pump for supplying fuel under pressure to "said nozzles, a fuel conduit communicating said pump with said nozzles and having a metering restriction therein upstream of the "nozzles, ad-

'justa'ble valve means for varying the flow through said restriction, manual means for adjusting said valve means, an engine driven governor operatively connected to'said valve means for automatically adjusting the latter, and means responsive to changes in the density of the air flowing to the engine arranged to adjust the fiow through said restriction independently of said governor.

35. In a system for feeding fuel to an engine. a conduit supplying fuel to said engine, a metering restriction in the conduit, means for regulating the pressure drop across the restriction, means for automatically varying the effective area of the restriction with changes in engine speed, and means for automatically varying the effective area of said restriction with variations of a temperature level in said engine.

36. In a system for feeding fuel to an engine, a conduit supplying fuel to said engine, a meterving restriction in the conduit, means for regulating the pressure drop across -means for automatically varying the effective the restriction,

area of the restriction with changes in engine 25 speed, and means'for automatically varying the 'efiective area of said restriction with variations of engine induction air pressure.

FERDINANDO CARLO REGGIO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,310,984 Mock et al. -Feb. 16, 1943 2,414,322 Mock ..1 Jan. 14,194! 2,581,275 Mock Jan. 1, 1952 2,581,276 Mock Jan. 1, 1952 

